Australia’s “60 Minutes” has broadcast an item called “Crunch Time” which made much of the opinions of David Evans, a computer programmer with a PhD in electrical engineering who once worked on a mathematical modeling program for the Australian Greenhouse Office. Dr Evans put two arguments to support his view that global warming is not caused by carbon emissions. Dr Evans first point was that, although carbon emissions have continued to increase, global temperatures have not increased for the last eight years. Here is the graph of global temperatures from the UK Met. Office’s Hadley Centre. It’s difficult to see Dr Evan’s evidence that temperatures have stopped going up.

Global temperatures from the UK Met. Office’s Hadley Centre

Dr Evan’s other argument is that there is no “greenhouse signature”. The signature that he says he has been searching for is greater warming of the troposphere over the tropics. Indeed, he said that if there was such a signature, he would accept that carbon emissions were causing global warming. Well. here is his “signature”:

The “signature” of greenhouse warming

What we’re looking for is the black line indicating high temperature in the upper middle of the second graph on the top row. Unfortunately, we can’t really demand that Dr Evans change his opinion of the basis of these graphs because he has been searching for the wrong thing. These tropical temperature graphs show that global warming is happening but tell us nothing about its cause. As we all know by now, greenhouse gases reflect heat back to the earth. This means that less heat gets through to the stratosphere above the greenhouse layer. So, the real signature of greenhouse gases is cooling in the stratosphere while the lower atmosphere is warming – which is exactly what we find:

Decreasing temperatures in the stratosphere

The first graph shows decreasing temperatures in the stratosphere. The others show less decrease at lower altitudes. The “60 Minutes” programme didn’t raise any real questions about global warming – the only real question is why did they broadcast such a one-sided view?

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3 comments

You are reading the graph wrong, there is no signature in it. A signature would be indicated by a dramatic red clump near the black line to clearly differentiate, or leave a signature, as opposed to the previous readings.

Secondly, the cooling comes from satellite readings. That temp graph you showed contains unreliable land readings (which are subject to all kinds of adjustments and do not reflect straight oberservation). Here is the objective satellite report:

This is not the place for a detailed discussion of the science. JunkScience.com (among others) has a very detailed discussion of this issue at http://www.junkscience.com/MSU_Temps/Warming_Look.html#UAH%20MSU
Suffice it to say that the graphs Mick refers to were produced by John Christy at the University of Alabama. He has since written in the US Climate Change Executive Program (and similarly elsewhere) “Previously reported discrepancies between the amount of warming near the surface and higher in the atmosphere have been used to challenge the reliability of climate models and the reality of human induced global warming. Specifically, surface data showed substantial global-average warming, while early versions of satellite and radiosonde data showed little or no warming above the surface. This significant discrepancy no longer exists because errors in the satellite and radiosonde data have been identified and corrected. New data sets have also been developed that do not show such discrepancies.”

Comment by Peter on August 18, 2008 at 11:23 am

By the way, also in the programme, the nuclear advocate James Lovelock was shown saying that “wind power cannot provide more than a tiny fraction of the energy needs of civilisation”. In fact, Ken Caldeira, a climate scientist at Stanford University’s Carnegie Institution, has shown that the total energy contained in wind is 100 times the amount needed by everyone on the planet.

Comment by Peter on August 18, 2008 at 12:09 pm

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